yep, all the same, as far as interchangability.
Later ones have the ADD system, as you mention - but you can put an ADD front diff on a non-ADD truck no problem, just permanently "fix" teh sliding rod in there and plug the vac lines.
but axles, gears, everything else is identical.

With 200+ Billion electrical parts, the world most complicated machine is inside your own skull.

Question Reality.
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'89 Rnr DLX "SR4.5", 32s w/ 5.29 locked f/r blah blah